These studies were designed to define the target cell for ethylene glycol monomethyl ether (EGME) action in the rodent testis, and to compare fluid production and protein secretory patterns in the testes of treated and control animals. Adult F344 rats were treated with 150 mg/kg/day, 5 day/week, and sacrificed 1, 2, 4, 7 or 10 days after the first dose. In the testes of treated animals, the most sensitive cells were the premeiotic and meiotic spermatocytes. As length of treatment continued, the younger transitional spermatocytes, and more pachytene spermatocytes, were affected. Early and late stage spermatids did not appear affected, nor was the visual appearance of spermatogonia changed by exposure to EGME. Fluid production, androgen-binding protein secretion and electrophoreograms of proteins found in the ligated rete testis were also unchanged by EGME, showing that these indices of Sertoli cell function were not affected by EGME. The histologic and biochemical data suggest that both early and late spermatocytes are targets for EGME in the testis, and that the Sertoli cells are relatively unaffected.